1. Technical Field
The technical field relates to an optical device structure comprising a layer of polyimide (PI) or its copolymer.
2. Description of the Related Art
Organic light emitting diodes (OLEDs) have been deemed as a rising star of flat panel displays or the lighting industry due to superior characteristics thereof including light weight, thin profile, self-luminescence, low power consumption, no requirement of a backlight source, no limitation of viewing angle and rapid response time etc. In order to be more competitive in the display and lighting markets, R & D units in the world invest a great deal of funds and human resources to improve device efficiency. In addition to the development of interior luminescent materials, exterior light outcoupling is also capable of improving device efficiency. However, the distinction of the refraction index between various layers in an OLED is large (mismatch of refraction index) which causes only 20% of light to be emitted from the front of the device. If light reflection and refraction at the interfaces between each layer is lowered and the light inside the device is outcoupled again by improving the refraction index of each layer, the luminous efficiency of the OLED can thus be improved. The addition of high/low-refraction-index layers or microparticles which contribute to light refraction to the device structure is popular. However, most of the high/low-refraction-index materials mainly comprise inorganic materials. The organic materials with high heat resistance are rarely used. Additionally, while subsequently fabricating an ITO conductive film on such organic materials, the problem of surface damage of the organic material when the ITO is deposited needs to be overcome. Also, since the requirement of low resistance and high penetration rate of the ITO also needs to be considered, the options of materials are quite constrained. Therefore, development of one kind of material with transparency, high heat resistance, a flat surface, simple fabrication and low cost is quite competitive and a top priority.